1. Field of the Invention
This invention relates generally to devices and methods for in vitro analysis of fluid flow (e.g., hemodynamics) on cells (e.g., endothelial cells). More specifically, this invention relates to a method of using a device that permits more than one different cell types to be physically separated within the culture dish environment, while the inner cellular surface is exposed to the simulated hemodynamic flow patterns.
2. Description of Related Art
Atherosclerosis is a vascular inflammatory disease characterized by lesion formation and luminal narrowing of the arteries. Endothelial cell (EC) and smooth muscle cell (SMC) regional phenotypes have significant implications in the progression of vascular disease. During early atherogenesis, the endothelium becomes activated, leading to increased adhesion molecule expression, permeability to lipoproteins and cytokine generation. Such environmental changes can influence SMCs to undergo “phenotypic switching” characterized by morphological changes, increased proliferation and migration, and decreased expression of defining quiescent SMC markers.
Atherosclerosis is further characterized by its focal development in large arteries at hemodynamically defined regions, such as at bifurcations that produce complex flow patterns. Atheroprone regions, susceptible to plaque formation, are subjected to low time-averaged shear stress and “disturbed” oscillatory flow patterns. In contrast, atheroprotective regions, which are less susceptible to plaque formation, are exposed to relatively higher time averaged shear stress and pulsatile laminar flow (13, 39). In regions of chronic disturbed flow, changes in EC phenotype, such as increased adhesion molecule expression, (i.e., vascular cell adhesion molecule 1 (VCAM-1), intercellular adhesion module 1 (ICAM-1), e-Selectin), and transendothelial permeability to low density lipoproteins (LDL), will effect the local signaling environment and can alter SMC phenotype, leading to proliferation, migration and the pathogenesis of atherosclerosis.
The factors controlling changes in SMC phenotype involving EC's and hemodynamic flow patterns are not fully understood. However, a hallmark of SMC phenotype switching in atherosclerosis is the suppression of contractile proteins that define the differentiated SMC, including SMMHC, SMαA, and myocardin.
To understand the role of shear stress on the endothelium in atherogenesis, in vitro models that expose ECs to a variety of shear stress conditions have been extensively studied. Since ECs can discriminate variations in flow patterns and are sensitive to both shear stress magnitude and time-varying features of hemodynamics, emulating in vivo flow environments appears to have a greater impression on recapitulating the in vivo phenotype of the endothelium. Additionally, few studies have shown the intricate interactions and cross-communications of ECs and SMCs in the presence of any type of flow, and no known studies to date have examined how in vivo-derived human hemodynamic forces on the endothelium regulate SMC phenotypic switching, as it is classically defined by the literature.